Local residents pitch idea for new 520 interchange

Seattle neighborhood advocates have conjured up a design concept they say may help break the political impasse over the plan to replace the Highway 520 Montlake interchange south of Husky Stadium.

The idea is to shift the busy interchange east, to a site now used by the Museum of History & Industry, which plans to move to South Lake Union in 2011. Either a new tunnel or a drawbridge would then be built connecting the highway to Montlake Boulevard Northeast and Northeast Pacific Street.

Such an alignment may be less upsetting to some neighbors than earlier proposals to expand the current Montlake interchange or put a new exit high above the Washington Park Arboretum.

There are no cost figures or engineering yet to show whether the new tunnel or drawbridge would work.

A small group of neighborhood representatives plan to meet today to discuss the new "East Montlake Interchange," and then on Tuesday, the state Department of Transportation will show drawings to a 33-member design-mediation panel.

"We have to move a little bit cautiously, and hope everything works out," said Rob Wilkinson, a Montlake resident, pitching the new approach.

The Montlake interchange is a big piece of the 520 puzzle. While the state wants to build a new six-lane bridge by 2018, there's a lack of funding and little consensus on its design. Political leaders have tried unsuccessfully since the 1980s to replace or expand the aging four-lane, Lake Washington floating bridge, built in 1963.

When the state previously proposed simply enlarging the 520 Montlake interchange to better accommodate traffic, homeowners complained about added noise and blight.

In response, Wilkinson and Jonathan Dubman, another Montlake resident, proposed the so-called "Pacific Interchange" in 2005, aiming to shift the bulky ramps offshore. A tall exit bridge would have run from Foster Island, over Union Bay, to Husky Stadium. The plan was reviled by Arboretum supporters.

The latest tunnel idea would require a steep grade, tight curves and a speed limit of 25 mph, said project director Ron Paananen. And the proposed drawbridge would encroach on the UW stadium's south entrance, as well as the university's Waterfront Activities Center.

"It gives us some concern, but nothing's off the table," said Scott Woodward, UW vice president for external affairs. He's awaiting details about how the exit, a Sound Transit rail tunnel and two major streets would function together, and where they all would converge near the stadium.

The mediation panel, representing government, environmental and neighborhood interest groups, is supposed to gather facts and send its plan for the interchange to Gov. Christine Gregoire by December.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com